This invention relates to newly identified polynucleotides, polypeptides encoded by such polynucleotides, the use of such polynucleotides and polypeptides, as well as the production of such polynucleotides and polypeptides. More particularly, the polypeptide of the present invention is a prostatic growth factor which is sometimes hereinafter referred to as “PGF”.
This invention relates to a polynucleotide and polypeptide molecules which are structurally and functionally related to TGF-β. The transforming growth factor-beta family of peptide growth factors includes five members, termed TGF-β1 through TGF-β5, all of which form homo-dimers of approximately 25 kd. The TGF-β family belongs to a larger, extended super family of peptide signaling molecules that includes the Muellerian inhibiting substance (Cate, R. L. et al., Cell, 45:685–698 (1986)), decapentaplegic (Padgett, R. W. et al., Nature, 325:81–84 (1987)), bone morphogenic factors (Wozney, J. M. et al., Science, 242:1528–1534 (1988)), vg1 (Weeks, D. L., and Melton, D. A., Cell, 51:861867 (1987)), activins (Vale, W. et al., Nature, 321:776–779 (1986)), and inhibins (Mason, A. J. et al., Nature, 318:659–663 (1985)). These factors are similar to TGF-β in overall structure, but share only approximately 25% amino acid identity with the TGF-β proteins and with each other. All of these molecules are thought to play an important roles in modulating growth, development and differentiation. The protein of the present invention, PGF, retains the seven cysteine residues conserved in the C-terminal, active domain of TGF-β.
TGF-β was originally described as a factor that induced normal rat kidney fibroblasts to proliferate in soft agar in the presence of epidermal growth factor (Roberts, A. B. et al., PNAS USA, 78:5339–5343 (1981)). TGF-β has subsequently been shown to exert a number of different effects in a variety of cells. For example, TGF-β can inhibit the differentiation of certain cells of mesodermal origin (Florini, J. R. et al., J. Biol. Chem., 261:1659–16513 (1986)), induced the differentiation of others (Seyedine, S. M. et al., PNAS USA, 82:2267–2271 (1985)), and potently inhibit proliferation of various types of epithelial cells, (Tucker, R. F., Science, 226:705–707 (1984)). This last activity has lead to the speculation that one important physiologic role for TGF-β is to maintain the repressed growth state of many types of cells. Accordingly, cells that lose the ability to respond to TGF-β are more likely to exhibit uncontrolled growth and to become tumorigenic. Indeed, the cells lack certain tumors such as retinoblastomas lack detectable TGF-β receptors at their cell surface and fail to respond to TGF-β, while their normal counterparts express self-surface receptors in their growth is potently inhibited by TGF-β (Kim Chi, A. et al., Science, 240:196–198 (1988)).
More specifically, TGF-β1 stimulates the anchorage-independent growth of normal rat kidney fibroblasts (Robert etal., PNAS USA, 78:5339–5343 (1981)). Since then it has been shown to be a multi-functional regulator of cell growth and differentiation (Sporn et al., Science, 233:532–534 (1986)) being capable of such diverse effects of inhibiting the growth of several human cancer cell lines (Roberts et al., PNAS-USA, 82:119–123 (1985)), mouse keratinocytes, (Coffey et al., Cancer RES., 48:1596–1602 (1988)), and T and B lymphocytes (Kehrl et al., J. Exp. Med., 163:1037–1050 (1986)). It also inhibits early hematopoietic progenitor cell proliferation (Goey et al., J. Immunol., 143:877–880 (1989)), stimulates the induction of differentiation of rat muscle mesenchymal cells and subsequent production of cartilage-specific macro molecules (Seyedine etal., J. Biol. Chem., 262:1946–1949 (1986)), causes increased synthesis and secretion of collagen (Ignotz et al., J. Biol. Chem., 261:4337–4345 (1986)), stimulates bone formation (Noda et al., Endocrinology, 124:2991–2995 (1989)), and accelerates the healing of incision wounds (Mustoe et al., Science, 237:1333–1335 (1987)).
Further, TGF-β1 stimulates formation of extracellular matrix molecules in the liver and lung. When levels of TGF-β1 are higher than normal, formation of fiber occurs in the extracellular matrix of the liver and lung which can be fatal. High levels of TGF-β1 occur due to chemotherapy and bone marrow transplant as an attempt to treat cancers, eg. breast cancer.
A second protein termed TGF-β2 was isolated from several sources including demineralized bone, a human prostatic adenocarcinoma cell line (Ikeda et al., Bio. Chem., 26:2406–2410 (1987)). TGF-β2 shared several functional similarities with TGF-β1. These proteins are now known to be members of a family of related growth modulatory proteins including TGF-β63 (Ten-Dijke et al., PNAS-USA, 85:471–4719 (1988)), Muellerian inhibitory substance and the inhibins. Due to amino acid sequence homology, it is thought that the PGF polypeptide of the present invention is also a member of this family of related growth modulatory proteins. However, to date, this polypeptide has only been found by the inventors to be present in the prostate.